CHICAGO — Fans at Wrigley Field were treated to a one-of-a-kind play Thursday evening.

The New York Mets scored a run on a controversial — and confusing — sequence against the Chicago Cubs in the top of the first inning.

With runners on second and third base and only one out, Cubs pitcher Shota Imanaga induced a popup from Mets DH Mark Vientos that drifted into foul territory down the left field line.

Cubs shortstop Dansby Swanson and third baseman Matt Shaw converged on the popup and as Swanson made the catch, he tripped over Shaw’s foot and careened toward the stands.

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Since MLB guidelines in stadiums have changed in recent years, there was a net blocking Swanson’s path into the first row of seats.

As he fell into the net, he flipped the ball to Shaw, who fired home. Mets shortstop Francisco Lindor had tagged up from third base and was attempting to score.

Shaw’s throw beat Lindor by a sizeable margin, but the umpires overruled the play and granted Lindor home plate. The explanation was Swanson’s momentum carried him out of play, meaning it is a dead ball and both runners move up a base as a result.

It was a truly wild sequence:

The Cubs challenged the play, but the call on the field was confirmed.

“First of all, you’re taking a chance because they scored a run,” Cubs manager Craig Counsell said after the game. “So it’s worth an ask because they scored a run on the play. The netting causes problems with that play. In the end, it’s the umpires’ judgment: Was he in the stands? I mean, he’s not in the stands because there’s a net there. His butt’s on the on the railing.

“But in [third base umpire] DJ [Reyburn’s] opinion he was in the stands.”

The Mets later scored another run when the next hitter, left fielder Brandon Nimmo, lined a two-out RBI single to right field.

So, what could have been an inning-ending double play turned into two runs for the Mets in what ended up as a major momentum swing in the game.

[PCA ready for October stage at Wrigley Field]

The teams split the first two games of the series, with the Mets picking up a come-from-behind victory Tuesday night while the Cubs enjoyed a blowout win Wednesday evening.

The Cubs’ magic number is two to lock up the top NL Wild Card spot and host the first-round series at Wrigley Field next week against the San Diego Padres.